Is there a way to switch focus to the image window without having to click it?

Is there a way to switch focus to the image window without having to click it?

If I'm editing an image and I click the toolbox (or, say, the docked layers dialogue), if I hover my cursor back over the image and press and hold spacebar so I can scroll around the image, currently I have to click within the image window before it registers my keystroke.

Is there a way around this?

The more intuitive behaviour and what I want to be able to do is just hover my mouse cursor over a window and and keystrokes or scrolling I perform happen within that window. This currently happens if I scroll using my mouse scroll wheel, but not with keystrokes.

I'm using single window mode in Gimp 2.8, though I've also experienced this issue in non-single window mode when using Gimp 2.6.